Seeds contain a variety of proteins that function primarily to provide storage reserves or defense functions against pests and pathogens. Maize ribosome-inactivating protein 1 (RIP 1) is an abundant seed protein with a putative role in plant defense. RIP 1 readily inactivates ribosomes from non-plant eukaryotes but has little activity against ribosomes from plant species. RIP 1 was tested for antifungal activity in a microculture assay. Conidia were treated with RIP1 or control proteins and monitored for abnormal growth or morphology over time. Fungi from the genera Aspergillus exhibited a strong response to RIP1. Aspergillus flavus, a maize pathogen which produces aflatoxin B1, had an increase in hyphal branching after RIP1 protein treatment that was not observed in control protein treatments. Quantitative analysis confirmed that the branching phenotype was significant. The chitin binding dye Congo red was used to show that branched hyphae treated with RIPl had only one actively growing hyphal tip whereas the few control hyphae with branching had multiple growing hypal tips. The genetically well characterized but non-pathogenic species Aspergillus nidulans was also tested in the microculture assay. A striking decrease in the number and growth of hyphae was observed when A. nidulans conidia were treated with RIP1 protein. The changes in growth of A. flavus and A. nidulans are consistent with maize RIP1 having antifungal activity.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)